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THE ZOOCECIDIA OF NORTHEASTERN 

UNITED STATES AND EASTERN 

CANADA 



A DISSERTATION 

SUBMITTED TO THE FACULTY 

OF THE OGDEN GRADUATE SCHOOL OF SCIENCE 

IN CANDIDACY FOR THE DEGREE OF 

DOCTOR OF PHILOSOPHY 

DEPARTMENT OF BOTANY 



BY 

BERTRAM WHITTIER WELLS 



Private Edition, Distributed By 

THE UNIVERSITY OF CHICAGO LIBRARIES 

CHICAGO, ILLINOIS 



Reprinted from 

The Botanical Gazette, Vol. LXV, No. 6 

June, 1918 



Ube mniversttE of dbtcaao 



THE ZOOCECIDIA OF NORTHEASTERN 

UNITED STATES AND EASTERN 

CANADA 



A DISSERTATION 

SUBMITTED TO THE FACULTY 

OF THE OGDEN GRADUATE SCHOOL OF SCIENCE 

IN CANDIDACY FOR THE DEGREE OF 

DOCTOR OF PHILOSOPHY 

DEPARTMENT OF BOTANY 



BY 

BERTRAM WHITTIER WELLS 



Private Edition, Distributed By 

THE UNIVERSITY OF CHICAGO LIBRARIES 

CHICAGO, ILLINOIS 



Reprinted from 

The Botanical Gazette, Vol. LXV, No. 6 

June, 1918 






i sity 



THE ZOOCECIDIA OF NORTHEASTERN UNITED STATES 
AND EASTERN CANADA 

CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 239 

B. W. Wells 

This summary is based upon a completed descriptive account 1 
of the zoocecidia of the region studied, which is that phy to- 
geographic region dealt with by Gray's New Manual of Botany 
(7th ed., 1908). The only similar general statement preceding this 
is that of Felt (4), who has presented some approximate figures 
from an entomological standpoint pertaining to American insect 
galls. The mite (Eriophyidae) galls were not included in his 
discussion. 

Historical 

Three local studies of zoocecidia have been made which deserve 
mention in a brief historical account. Cook (2) in 1904 published 
the description of 66 galls from Indiana. Jarvis (7) in 1908 
presented a catalogue of the insect galls of Ontario, comprising 221 
species. Stebbins (10) in 1910 described 205 species of galls 
collected in the vicinity of Springfield, Massachusetts. A post- 
humous catalogue of 233 southern New England galls by Thompson 
(11) appeared in 1915, edited by Felt. This also included a 
summary of American Cynipidae galls, listing 350 species. 

For the sake of comparison a short summary of the European 
work will be given. Haimhoffen (5) in 1858 presented 350 as the 
number of zoocecidia for central Europe. Schlechtendal (9) in 
189 1 listed 13 15 insect, mite, and nematode galls on the plants of 
Germany. Kieffer (8) in 1901 published a synopsis of the 
zoocecidia of Europe. There also appeared the same year a more 
exhaustive study in Darboux and Houard's (3) systematic 

1 The work contains the description of 792 nematode, mite, and insect galls; half 
of this number will be supplemented by illustrations. Keys to the galls on the various 
plant genera have been made, the plant genus constituting the unit by which the galls 
have been grouped. 

535] [Botanical Gazette, vol. 65 



536 BOTANICAL GAZETTE [juxe 

catalogue of the zoocecidia of Europe and the basin of the Mediter- 
ranean, a work which in 1908 (supplement 19 13) was expanded by 
Houard (6) into the largest systematic cecidological work in exist- 
ence. This final general European work comprises the description 
of 1950 zoocecidia. 

Basis and plan of work 

The data from which the following summary is drawn were 
obtained during a period of 4 years, in which field studies in Con- 
necticut, Ohio, and Kansas were supplemented by a thorough 
canvass of the highly scattered cecidological literature. 

It may be of interest to mention the simple' and, it is believed, 
practical scheme which has been followed in the arrangement of the 
792 types described. The plant genus was made the unit under 
which the galls were grouped. This is in contrast to Houard's 
plan; he used the species, a plan which necessitated a vast amount 
of repetition, since innumerable galls occur on more than one species 
within the genus. It is a striking fact that very few galls are found 
upon more than one genus. In the study of the galls of the north- 
eastern United States, data concerning the plant species bearing 
the gall have been included with the descriptive material. To 
assist in locating the descriptions, keys were worked out for the 
genera having more than 6 or 8 species. A brief bibliography 
presenting the most important references was appended to each 
description. 

The plant genera in the work have been arranged alphabetically. 
The galls under each genus have been aggregated according to the 
classification of the cecidozoons. It is thus evident that artificial 
classification has been pursued throughout. At the present time 
any classification of zoocecidia must be artificial. The morpholog- 
ical data available, particularly of an anatomical nature, are far 
too meager to make possible anything approaching a natural 
classification. 

Summary of numerical data 

In the case of all of the following figures presented, it should be 
understood that they are but approximations. So new is the field 
of systematic zoocecidology in America, and so incomplete and 



1918] WELLS—ZOOCECIDIA 537 

unsatisfactory are the data in innumerable specific instances, that 
at the present time any generalizations of a numerical nature 
cannot be accepted as expressing the exact condition. 

A tabulated statement of the 792 galls known from the north- 
eastern quarter of the United States and eastern Canada, according 
to the cecidozoon orders and families, is as follows: 

DISTRIBUTION BY ANIMAL FAMILIES 

Nematoidea (Nematohelminthes) Gelechiidae 3 

Anguillulidae 2 Elachistidae 2 

Acarida (Acarina) Sesiidae 1 

Eriophyidae 87 Tortricidae 2 

Hemiptera (Insecta) Unclassified 10 

Aphididae 70 Diptera 

Psyllidae 6 Trypetidae 7 

Jassidae . 1 Itonididae 383 

Coleoptera Hymenoptera 

Cerambycidae 2 Chalcidae 2 

Buprestidae 1 Tenthridinidae 13 

Lepidoptera Cynipidae 194 

Tineidae 1 

As Felt has pointed out, the family containing the most gall 
makers is the Itonididae, embracing in our region 47 per cent of the 
gall biota. The Cynipidae follow with 37 per cent. The other 
families are represented by much smaller percentages, the Coleop- 
tera being barely represented with 3 ill-defined galls. 

The distribution of the galls (except nematode) by the plant 
families on whose members they occur is as follows. The families 
are arranged in the sequence given in Gray's Manual. 

DISTRIBUTION BY PLANT FAMILIES 

Pinaceae 13 Aristolochiaceae 2 Rosaceae 70 

Typhaceae 1 Polygonaceae 2 Leguminosae 18 

Gramineae 5 Chenopodiaceae 5 Euphorbiaceae 4 

Cyperaceae 1 Nyctaginaceae 1 Anacardiaceae 10 

Juncaceae 1 Portulacaceae 1 Aquifoliaceae 1 

Liliaceae 9 Ranunculaceae 7 Celastraceae 1 

Iridaceae 1 Magnoliaceae 2 Aceraceae 14 

Salicaceae 60 Lauraceae 5 Balsaminaceae 3 

Juglandaceae 64 Papaveraceae 1 Rhamnaceae 2 

Betulaceae 18 Cruciferae 1 Vitaceae 20 

Fagaceae 183 Saxifragaceae 5 Tiliaceae 7 

Urticaceae 37 Hamamelidaceae 7 Malvaceae 1 



538 BOTANICAL GAZETTE [June 

DISTRIBUTION BY PLANT FAMILIES — Continued 

Hypericaceae 2 Ericaceae 17 Labiatae 14 

Violaceae 2 Primulaceae 1 Solanaceae 3 

Cactaceae 1 Ebenaceae 2 Scrophulariaceae 2 

Lythraceae 1 Oleaceae 6 Bignoniaceae 1 

Onagraceae 1 Apocynaceae 1 Rubiaceae 3 

Araliaceae 1 Asclepiadaceae 2 Caprifoliaceae 16 

Umbelliferae 1 Convolvulaceae 1 Compositae 121 

Cornaceae 1 1 Verbenaceae 3 

The striking fact brought out by this list is the extreme irregu- 
larity of the distribution. Many of the larger families have few or 
no galls, while on the other hand a few of the smaller families, 
particularly the Fagaceae, possess many cecidia. Quercus alone 
has 176 galls, of which 157 are cynipid types. Felt presents 277 
as the approximate figure for the cynipid galls on the American 
oaks. The Cynipidae- Quercus situation in Europe as well as in 
America presents the most striking example of gall evolution within 
a single genus of plants related to a comparatively few (9 or 10) 
closely related genera of insects. 

It is worthy of note that such large families as the Caryophyl- 
laceae, Cruciferae, and Boraginaceae contain no gall-bearing species. 
The Umbelliferae possess but a single gall. The widely distributed 
tree species Platanus occidentalis does not bear any zoocecidia. 

The problem in distribution on the plants presented by the 
preceding list is an exceedingly difficult one and probably cannot 
be answered on the basis of the physiological information at present 
available. This intimate and constant relation between specific 
insects and specific plants forms one of the most significant phenom- 
ena in the field of cecidology. 

As far as data were obtainable, figures were worked out indi- 
cating the distribution of the galls on the plant parts, with the 
following result: 

DISTRIBUTION ON PLANT PARTS 

On leaf blade (of these 52 are "blis- On roots 12 

ter" galls) 427 On flowers v . 27 

On petiole (most of these occur also From buds forming a rosette type ... 47 

on blade) 47 From buds forming a solid concentric 

On stem (8 per cent of these occur type 3° 

also on the leaf) 208 



1918] WELLS—ZOOCECIDIA 539 

Slightly over half of the galls (53 per cent) occur on the leaf 
blade. This fact is of course related to the relatively large amount 
of embryonic leaf tissue exposed in the early stages of shoot develop- 
ment. In the cases of the stem, root, and bud galls numerous 
factors enter, but perhaps the most important is the factor of insect 
equipment necessary to place the larval cecidozoon in contact with 
the meristematic tissues. 

Some figures pertaining to gall structure were obtained which 
are of interest. A few words of explanation are necessary before 
presenting the tabulation. Under the monothalamous galls were 
included those types which, so far as could be determined, are 
generally one-chambered, that is, the gall never is a structure 
constantly characterized by the confluence of the walls of two or 
more chambers as in the polythalamous condition. A few species 
are intermediate and were classified in the direction in which it was 
believed they leaned the more strongly. A number of galls, such 
as the erineum (hypertrophied epidermal cells) types, do not fall 
in either of the above categories and cannot be included in such a 
classification. 

In those cases in which sufficient data were available, an attempt 
was made to study the galls on the basis of Kuster's division of 
cecidia into kataplasmas and prosoplasmas. By " kataplasmas " 
KusTER means those indefinite, indeterminate galls whose structure 
is developed through hyperplasia of embryonic tissue, the end 
product not becoming in its differentiation, orientation, and form 
of tissues fundamentally different from the normal plant part. 
"Prosoplasmas," on the other hand, are highly definite and deter- 
minate galls whose structure differs fundamentally from the normal 
plant, the tissues in their form and orientation characters con- 
stituting an aggregation of new qualities. These two groups 
intergrade, but the intergrading forms are relatively few in number 
and were classified according to what was believed to be the 
predominating condition. In all cases where data were not suffi- 
cient to pass judgment, the gall was omitted from the census. 

Another set of figures presented is that based on Kuster's 
classification of galls into organoid and histoid types. An 
"organoid" gall is one in which an entire plant organ (leaf, stem, 



540 BOTANICAL GAZETTE [june 

internode, ovulary, etc.) as a unit suffers modification without a 
fundamental change in its morphology. The "histoid" galls are 
those more numerous types in which an entire plant organ is not 
involved, the gall being more or less definitely appendicular. This 
group includes all of the prosoplasmas and part of the kataplasmas. 

DATA BASED ON NUMBER OF CHAMBERS 

Monothalamous galls 4°S 

Polythalamous galls 134 

Non-chambered galls 67 

Insufficient data to classify 183 

The excessively large number of monothalamous forms is a fact 
related to the character of oviposition. If the eggs are habitually 
deposited in an aggregate manner, a polythalamous gall is almost 
certain to result, although there are striking exceptions to this. 
The great majority of larvae, however, begin their gall-making 
activity at sufficient distance apart to develop the common mono- 
thalamous types of cecidia. 

KATAPLASMAS AND PROSOPLASMAS 

Kataplasmas 395 

Prosoplasmas 3 22 

Insufficient data to classify 73 

Viewed from an evolutionary standpoint, the kataplasmas 
represent the lower levels and the prosoplasmas the higher. That 
the latter have undergone a considerable expansion indicating 
relatively rapid progress in recent geologic time is evidenced by the 
relatively large number of prosoplasmas. 

ORGANOID AND HISTOID GALLS 

Organoid 215 

Histoid 495 

Insufficient data to classify 82 

These figures have no special significance, perhaps, other than 
the indication of differences in the range of the gall stimulus. In 
the organoid types the stimulus is diffused over relatively large 
areas, inciting all of the tissues of one organ to hypertrophy and 
hyperplasia. In the histoid forms the stimulus only affects those 
tissues in a restricted area about the cecidozoon, these tissues 
responding in a definite and striking manner. 



1918] WELLS—Z00CEC1DIA 541 

In addition to the above two tables Kuster has, in his classifica- 
tion of cecidia, furnished the basis for another table in his analysis 
of the prosoplasmas. These he divides into four groups: the leaf 
edge "roll" galls; the diverticulum or outpouching types; the 
"walled" (umwallungen) forms, whose walls grow up about the 
superficial larva; and the concentric (mark) cecidia whose larvae 
inaugurate gall formation from a point within the tissue. In the 
following list this classification was extended to include so far as 
possible the kataplasmas also, since a great many of these latter 
galls can properly be placed under some one of the preceding four 
groups. The 58 "rosette" and the 28 erineum types cannot be 
included. 

NUMBERS OF VARIOUS GALL TYPES 

Leaf edge "roll" types 32 Concentric types 

Diverticulum types 0n leaves 145 

On stems 184 

On other parts 36 

Galls unclassifiable in the above cate- 



Leaf or leaflet fold along mid- 
vein 19 



Pouch types proper 109 gories 86 

Walled (umwallungen) types 87 Unclassified through insufficient data 94 

The factors entering into the production of these various kinds 
of galls are many; a full discussion of them cannot be presented 
here. Attention, however, should be called to the two main groups, 
namely, those which are related to the plant and those related to 
the cecidozoon. The diverticulum galls are, with few exceptions, 
only known from the leaf, particularly the blade, since this organ 
only is sufficiently free from stereome tissues to make possible the 
characteristic pouching out on the side opposite the cecidozoon. 
The walled and concentric types can occur on any part of the plant, 
the latter constituting a much larger aggregation than any of the 
other kinds. Oviposition within the plant tissue or a migration 
inward on the part of the larva is necessary for the production of 
the concentric type of gall. Even in these cases constituting the 
highest galls, plant factors can exert a modifying influence. The 
study of the relative importance of the two groups of factors 
entering into cecidium morphogenesis in specific cases is one of the 
most valuable and suggestive in the field of zoocecidology. 

University of Arkansas 
Fayetteville, Ark. 



542 BOTANICAL GAZETTE [june 

LITERATURE CITED 

i. Connold, E. T., British vegetable galls. New York. 1902. 

2. Cook, M. T., The insect galls of Indiana. 29th Ann. Rept. Dept. Geol. 
and Natural Hist. Indiana, pp. 801-867. 1904. 

3. Darboux, and Hotjard, C, Catalog systematique des Zoocecidies de 
l'Europe at du Bassin mediterranee. Paris, igoi. 

4. Felt, E. P., American insect galls. Ottawa Nat. 30:37-39. 1916. 

5. Haimhoffen, G. R., Beobachtungen iiber die Menge und das Vorkommen 
der Prlanzengallen und ihre spezielle Verteilung auf die verschiedenen 
Pflanzengattungen und Arten. Verhandl. Zool.-Bot. Gesell. 8:285. 1858. 

6. Houard, C, Les Zoocecidies des Plantes d'Europe et du Bassin de la 
Meditteranee. 2 vols. Paris. 1909. Vol. 3, Paris. 1913. 

7. Jarvis, T. D., A catalog of the gall insects of Ontario. 39th Ann. Rept. 
Ent. Soc. Ont. 70-98. 1908. 

8. Kieffer, J. J., Synopsis des Zoocecidies d'Europe. Ann. Soc. Entom. 
France. 70:233-384. 1901. 

9. Schlechtendal, D. H. R. v., Gallbildungen (Zoocecidien) der deutschen 
Gefasspflanzen. Zwickau. 1891. 

10. Stebbins, F. A., Insect galls of Springfield, Mass., and vicinity. Bull. 
2. Springfield Mus. 19 10. 

11. Thompson, M. T., An illustrated catalog of American insect galls. Edited 
by E. P. Felt. Nassau, N. Y. 1915. 



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